Maternal sera (MS) taken from 1396 women prior to chorionic villus sampling at 9–12 menstrual weeks were assayed for unconjugated oestriol (uE3) and alpha-fetoprotein (AFP). Median levels increased by 41 and 26 per cent per week respectively in normal pregnancies. There were 32 pregnancies with a chromosome abnormality. The median MS uE3 and AFP were 0.73 and 0.75 multiples of the median (MoM) respectively in the ten cases of Down's syndrome (DS) but not decreased in the other abnormalities. These results suggest that both uE3 and AFP may be useful in identifying DS in the first trimester. Additional prospective studies are needed to confirm these findings. 相似文献
We assayed maternal serum samples from 134 black and 268 white women from 16 to 18 weeks of gestation for intact human chorionic gonadotropin (hCG), and unconjugated oestriol (uE3). Serum from women with high ( ⩾ 2·5 MOMs) or low (risk for Down syndrome ⩾ 1/365) maternal serum alpha-fetoprotein (MSAFP) levels were excluded. After correcting for maternal weight, we found that median hCG levels were 16 per cent higher in black women but uE3 levels were not significantly different. These results confirm three other studies for hCG and one study for uE3. Corrections are recommended for both maternal serum hCG and AFP before calculating the risk for Down syndrome in black women. 相似文献
We investigated the fatty acid compositions and concentrations of wild marine fish larvae with a highly accurate method because our knowledge of them has been seriously limited compared with cultured larvae. This study presents estimates of the fatty-acid-based nutritional condition of individual larvae in the field. Because the pointhead flounder Cleisthenes pinetorum displays relatively high stock size fluctuations, we investigated the developmental change in the fatty acid compositions of the body trunk, head, and eye and the annual fluctuations in the fatty acid concentrations in the trunk. We show that the process of fatty acid accumulation is not uniform across body parts and that the trunk is a better indicator of larval nutritional status than other parts because there is less time lag. Starved larvae with simultaneously high docosahexaenomic acid ratios and low total fatty acid concentrations, as observed in laboratory experiments, are rare in the wild. Thus, starved larvae must be removed rapidly by predators before they can experience a relatively long period of starvation in the wild. Fatty acid accumulation was greater in the larvae of the 2005 year class than in those of the 2006 year class in their first feeding stage, according to the optimal model derived with generalized linear model. A previous study indicated that the 2005 year class showed stronger recruitment than the 2006 year class. We conclude that the fatty acid analysis of wild larvae is a useful index of their nutritional status and mortality, especially in the first feeding stage. 相似文献
Journal of Material Cycles and Waste Management - Open burning is a waste management practice performed by many people worldwide, especially in developing countries. Lack of detailed data of open... 相似文献
Recovering fluorine from end-of-life products is crucial for the sustainable production and consumption of fluorine-containing compounds because fluorspar, an important natural resource for fluorine, is currently at a supply risk. In this study, we investigated the feasibility of chemically recycling a fluorine-containing photovoltaic (PV) backsheet for fluoropolymer recycling. Herein, a PV backsheet consisting of laminated polyethylene terephthalate (PET) and polyvinylidene fluoride (PVDF) was treated with different concentrations of sodium hydroxide (NaOH) to hydrolyze the PET layer to water-soluble sodium terephthalate (Na2TP) and to separate pure PVDF layer as a solid material. Optimized alkaline conditions (up to 10 M NaOH at 100 °C for 2 h) were determined, under which 87% of the PET layer could be decomposed without any significant deterioration of the PVDF layer. The hydrolysis kinetics of PET layer in NaOH could be explained by the modified shrinking-core model. Considering that the mass of end-of-life PV panels in Japan is estimated to increase to approximately 280,000 tons per year by 2036, PV backsheets are attractive candidates for fluoropolymer recycling, which can be effectively achieved using chemical recycling approach demonstrated in this study.
Environment, Development and Sustainability - Many information and communications technology (ICT) services have become commonplace worldwide and are certain to continue to spread faster than... 相似文献
Journal of Material Cycles and Waste Management - In this study, we conducted bench-scale investigations for the recovery of Cu wires, PVC coatings, and plasticizers from long non-uniform cables by... 相似文献
In this study, poly-lactic acid (PLA) and poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH) were pyrolyzed at various temperatures (300, 350, 400, 500, 600, and 700 °C) and heating rates (5, 10, 20, 30, and 40 °C min−1) using a pyrolysis–gas chromatograph/mass spectrometer (Py–GC/MS). The results revealed that the main pyrolysis products of PLA were acetaldehyde, lactide (including meso-lactide and d-, l-lactide), and oligomers. Crotonic acid and its oligomers accounted for most of the PHBH pyrolyzates. The pyrolysis temperature significantly correlated with the product distribution, but the heating rate had a small effect on the product distribution. Lactide and crotonic acid were two kinds of high-value chemicals, and their highest yields were obtained at 400 and 600 °C with 29.7 and 72.6 area %, respectively. Secondary reactions could not be neglected at 700 °C, and acetaldehyde and crotonic acid decreased to 65.0 and 69.6 area %, respectively. These results imply that pyrolyzate selectivity can be controlled by temperature management during pyrolysis.
